With the constant progress of radio technology, the generalization of various intelligent terminals and the growth of data service, the amount of mobile communication traffic will have a 1-fold increase per year in the future, and the research target of the METIS (Mobile and Wireless Communications Enablers for the Twenty-Twenty Information Society) with relation to 5G mobile communication technology has been established: the data service will grow 1000 times within 10 years in the future.
The current 4G system has used a plurality of technologies, including: OFDM, (Orthogonal Frequency Division Multiplexing), MIMO (Multiple Input Multiple Output), MU-MIMO (Multi-User MIMO), and HARQ (Hybrid Automatic Repeat reQuest), aiming at improving the frequency spectrum efficiency of cells, and improving the system capacity of a specific cell through a small cell technology. However, these technologies still can not satisfy the requirement for the exponential increase of the 5G communication data volume.